It does have a 1-10 resistance setting dial. I usually have it at 7. Any idea what distance 300-500 strokes approximates to?
Using a Concept 2 rower, you are able to see your stroke rate and speed per 500 meters. Remember, the speed is the number you are aiming for, not the resistance scale. It's similar to racing a bicycle, it's about the gear you can use most efficiently over a set distance or time. Using a larger number will cause your muscles to fatigue earlier than you may like and your time will be slower than using a lower number but higher stroke rate. Most actual rowers use a level between 4 and 7 and a stroke rate between 26 and 35.
If you know someone who is a rower, ask them to look at your technique to ensure you are rowing correctly. There are number of good videos on YouTube or the Concept 2 site demonstrating proper technique.
A fun thing to measure is your running time for a distance compared to your rowing time for the same distance. Two miles (3200 meters), 5K, etc.
The idea of learning your desired drag factor is so you can set an individual rower to the same drag factor no matter where you are or which rower you are using so it will feel the same.